Frequency multiplier circuits



1936- H. GUTMANN 2,063,093

I FREQUENCY MULTIPLIER CIRCUITS I Original Filed March 6, 1931 I 1g INVENTOR HERBERT GUTMANN ATTo' NEY Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE FREQUENCY MULTIPLIER CIRCUITS Herbert Gutmann, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic 111. b. H., Berlin, Germany, a corporation of Germany 4 Claims.

This application is a division of my copending application Serial No. 520,541, filed March 6, 1931, entitled Circuit arrangement for electric amplifiers, which resulted in U. S. Pat. #1,985,923, on Jan. 1, 1935.

The object of this invention is to provide an amplifier arrangement, particularly for audio frequency and radio frequency amplification work which comprises two series-connected tubes of the same type. If both tubes are simultaneously supplied with grid potential of like value, such an arrangement results in the same slope and only half the plate reaction of a single tube. Hence, this circuit scheme results in the inverse condition obtained with the usual parallel connection in which, for two similar tubes, the slope is doubled while the plate reaction remains unchanged.

Series connection, of course, is useful also for more than two tubes as well as for tubes of different types. It could also be combined With parallel connection so that any desired plate reaction and any desired slope inside certain limits are obtainable.

Circuit schemes according to this invention may be used to advantage in cases where an existent grid alternating current potential is. to be amplified a certain amount and where a tube which possesses the plate reaction required therefor, due to its limited permissible plate direct current has such a narrow allowable grid swing that the available alternating current po tential cannot be accommodated under conditions free from distortion. In this case, according to this invention, two tubes with double plate reaction (whereby, double grid swing is permissible for the same plate potential) will then be connected in series. The assembly then presents the desired plate reaction. However, the joint plate potential must be doubled. This can be done without difficulties and harmful effects since it is distributed over the two tubes.

The circuit scheme here disclosed may be used to advantage for reception where it is desired to tune two circuits independently of each other to different band widths and where the incoming energy is to be combined again.

A third application of the circuit scheme here disclosed is for frequency doubling or frequency multiplication.

In describing my invention, reference will be made to the attached drawing in which I have shown merely for purposes of illustration, several circuit arrangements which include the novel features of my invention. In Figs. 1a and lb and in Fig. 2, I have shown the essential features of circuits for amplifying wave energy. The circuits of Figs. 1a and 1b are adapted to amplify waves of lower frequency than the circuit of Fig. 2. In Figs. 3a and 3b, I have shown circuit arrangements for amplifying and frequency multiplying wave energy. In Fig. 3a, two stages in cascade are shown. In Fig. 3b, regeneration is introduced. Figs. 1a and 1b illustrate a scheme comprising two tubes, though it holds good for any other number of tubes. The control grids of tubes I and II are connected to secondary windings L1 and L2, respectively, which are in turn coupled to a primary winding L, which may be energized by any alternating current potential to be amplified. The cathode of tube I is united with the anode of tube II. The plate potential supply VA has its positive pole connected by way of an inductance which may be the load or the primary of a transformer or a resistance with the plate of tube I, while the negative pole is united with the filament of tube II. In parallel relation to each tube is suitably provided a high impedance or the series combination comprising a resistance and capacity. In some cases the resistance may be replaced by an inductance coil. The resistance R1 and condenser C1 are connected as shown across the anode-to-cathode impedance of one tube, while the condenser C2 and resistance R2 are connected as shown across the impedance of the other tube. Condensers C1 and C2 insure that each tube receives the plate-filament potential required for the starting of a plate current. Resistances R1 and R2 make the time-constant of the circuit so high that the audio frequency variations of the lowest occurring frequency Will not occasion any appreciable discharges of the condensers. Furthermore, R1 and R2 are so chosen that they do not impair the amplification of the tube. Hence, R1 and R2 must be high compared with the internal resistance of the tube and also great compared with of the condensers at the lowest occurring frequency. Each of the tubes is provided with its own filament potential and, if necessary, also with independent grid biasing potential, the latter, in case of direct current filament supply; being obtained or derived from the filament cur-j rent, as shown in Fig. 1a, or for direct current and alternating current heating from a resist ance W1, W2 in the plate return lead as shown in Fig. lb.

In the circuit of Figure 2 a radio frequency amplifier is involved in which the input circuits L1 and L2 of the two series-connected electron tubes are tuned to different band widths.

In Figs. 3a and 3b, circuit arrangements for frequency multiplication of an alternating current wave are shown. In these circuits, the two tubes I and II acting as rectifiers are connected audion-fashion; that is, the grids are connected with the cathodes by way of high ohmic resistances R and R and the connections between the grids and the corresponding grid circuit coils include the condensers C and C. The two tubes are to be controlled in such a manner that one semi-cycle of the input oscillations is amplified in tube I and the other semi-cycle in tube II. If the assumption be made that the grid circuit coils L1 and L2 in coupled relation with the input circuit L are connected in the same sense, then the connections of the coil L2 must be transposed or crossed, e. g. the lower end of the coil is connected with the grid and the upper end with the multiplication is effected in a single stage.

cathode of tube II. However, in the case of tube I, the upper end of the grid coil L1 is associated with the grid and the lower end with the cathode. It will be understood that the same effect is obtainable if the two grid coils L1 and L2 are wound in opposition. In this case, the transposition of the connections of one grid coil is not necessary. In Fig. 3a, the frequency doubling in the second stage is repeated, so that in the output circuit in Fig 3a, a frequency four times greater than that at the input end is obtainable. Thus, Fig. 3a shows the manner in which frequency doubling may be continued in additional stages, as described in detail above. In Fig. 3b, frequency Here, the plate coil is caused to react inductively on the grid coils L1 and L2 and the plate circuit is tuned to the desired multiple of the fundamental or input frequency. In both arrangements, the transposition of the input circuit causes the fundamental and odd harmonics to compensate or cancel out in the output circuit. Energy which is an even harmonic of the fundamental frequency may be drawn from the output circuit. In both cases, due to the action of the rectifiers I and 2 and of the coil circuit connections, one tube acts on one-half the cycle of the wave and the other tube on the other half of the cycle of the wave.

I claim:

1. In a system for multiplying the frequency of radio frequency oscillations, a. pair of thermionic rectifier tubes each having an anode, a cathode and a control grid, circuits for applying said oscillations, the frequency of which is to be multiplied between the control grid and cathode of each tube, the phase of the applied oscillations being reversed by one of said circuits so that one of said tubes operates on one half cycle of'the applied oscillations while the other tube operates on the other half cycle of the applied oscillations, a connection between the cathode of one of said tubes and the anode of the other of said tubes, an output circuit connected between the anode of one of said tubes and the cathode of said other of said tubes, a circuit including series impedances and reactances connected in parallel with said output circuit and a connection between a point on said last circuit and the connection between said anode and cathode.

2. In a system for multiplying the frequency of radio frequency oscillations, a pair of thermionic tubes each having an anode, a cathode and a control grid, a circuit including inductances for applying said oscillations, the frequency of which is to be multiplied between the control grid and cathode of each tube, the phase of the applied oscillations being reversed by reversing the leads between one of said circuits and the control grid and cathode to which it is connected, a connection between the cathode of one of said tubes and the anode of the other of said tubes, an output circuit connected between the anode of said one of said tubes and the cathode of said other of said tubes, an inductance in said output circuit coupled to said first named inductances, a resistance connected to the anode of one tube, a resistance connected to the anode of the other tube, and separate capacities connecting said resistances to said connection between the cathode of said one tube and the anode of said other tube.

3. A system for multiplying the frequency of radio frequency oscillations comprising, a pair of thermionic tubes each having an anode, a cathode and control grid, a circuit for applying said oscillations, the frequency of which are to be multiplied between the control grid and cathode of each tube, the phase of the applied oscillations being reversed by reversing the connection between one of said circuits and the grid and cathode to which it is connected, a direct connection between the cathode of one of said tubes and the anode of the other of said tubes, an output circuit connected between the anode of said one of said tubes and the cathode of said other of said tubes, a variable condenser in shunt with said output circuit, a circuit including series impedances and reactances in parallel with said output circuit, and a connection between a point on said last named circuit and said direct connection between the cathode of said one tube and the anode of the other tube.

4. A system for multiplying the frequency of radio frequency oscillations comprising, a pair of thermionic tubes each having an anode, a cathode and a control grid, circuits including reactances for applying said oscillations, the frequency of which are to be multiplied between the control grid and cathode of each tube, the phase of the applied oscillations being reversed by reversing the connection between one of said circuits and the grid and cathode to which it is connected, a direct connection between the cathode of one of said tubes and the anode of the other of said tubes, an output circuit connected between the anode of said one of said tubes and the cathode of said other of said tubes, a variable condenser in parallel with said output circuit, an inductance in said output circuit coupled to said first named inductances, and an impedance and capacity connected between the anode and cathode of each tube.

HERBERT GUTMANN. 

